JPH01183606A - Photodetecting device - Google Patents

Abstract

PURPOSE:To obtain the photodetecting device having a high optical coupling efficiency, and also, being miniature by providing a concave reflection mirror having a desired concave surface by inclining it against the photodetecting surface of a photodetector which has been placed on a circuit board, so as to be opposed to an emission end face of an optical fiber. CONSTITUTION:A light beam which has been emitted like a conical body using a horizontal axis as an axis from an emission end face of an optical fiber 10 is projected to a concave surface 21 of a concave reflection mirror 20, and reflected in the direction of a photodetector 1 thereby. In this case, the concave reflection mirror 20 has, for instance, a desired concave surface 21 such as a paraboloid of revolution, therefore, a reflected light is condensed to the photodetecting surface 3 of the photodetector 1. That is, since the reflected light is condensed to the photodetecting surface 3, even in case of a narrow and small photodetecting surface, the optical coupling degree of the optical fiber 10 and the photodetector 1 is high. Also, the optical fiber 10 can be installed adjacently in parallel to a circuit board 5, therefore, comparing with the case when the axis center of the optical fiber has been mounted vertically to the surface of the circuit board 5, the mounting work is facilitated, and also, the photodetecting device is miniaturized.

Description

[Detailed Description of the Invention] [Summary] Regarding a light receiving device that optically couples an optical fiber and a light receiving element, the purpose of the present invention is to provide a light receiving device that has high optical coupling efficiency and is small in size. and on a circuit board parallel to the optical fiber, in order to receive the light emitted from the optical fiber,
A device including a light-receiving element with a light-receiving surface facing upward, in which a concave reflecting mirror having a desired concave surface is installed facing the output end face of the optical fiber so as to be inclined in the direction of the light-receiving surface. shall be.

[Industrial application field]

The present invention relates to a light receiving device that optically couples an optical fiber and a light receiving element.

In recent years, light receiving devices have been provided in which an electric circuit such as a receiving circuit and a light receiving element are provided on the same circuit board.

At this time, if the optical signal transmission path and the electrical signal line are perpendicular to each other, there is a risk that the entire device will become larger.

Therefore, so-called flat-mounted light-receiving devices are becoming popular, in which a circuit board provided with an electrical signal path and an optical transmission path are installed in parallel.

On the other hand, in order to improve frequency characteristics, the capacitance of the light receiving element is made as small as possible. As a result, the light-receiving surface of the light-receiving element becomes smaller, and the degree of optical coupling decreases.

Accordingly, there is a need for a light-receiving device in which an optical signal is efficiently incident on a light-receiving element.

[Conventional technology]

FIG. 4 is a side sectional view of a conventional example in which an optical fiber and a light receiving element are mounted in a plane-mounted manner. In FIG. 4, reference numeral 5 denotes a circuit board made of ceramics or the like, on which a desired electric circuit and a light-receiving element 1 such as a photodiode are mounted, and which is firmly fixed to the surface of the base 6. It is.

The light-receiving element 1 is a chip-type element having a light-receiving surface 3 on the upper surface, and has an electrode provided on the entire back surface, and the electrode is closely connected to a pattern 4B provided on the surface of the circuit board 5. . Further, another ring-shaped electrode 2A is provided on the periphery of the light-receiving surface 3, and the electrode 2A is connected to a pattern 4A that is another electric signal path.

That is, the light-receiving element 1 has the light-receiving surface 3 facing upward and the circuit board 5
It is mounted on the circuit board 5 parallel to the upper surface of the circuit board 5.

Reference numeral 10 denotes a single mode optical fiber, which is an optical transmission line through which an optical signal is input to the light receiving element 1.

The end face of the optical fiber 10 is not a flat surface perpendicular to the axis, but is processed into an inclined end face 11 that is inclined at approximately 45 degrees with respect to the axis.

7 is a fiber holding stand provided with, for example, a V-shaped groove so as to horizontally support the optical fiber 10.

With the inclined end surface 11 of the optical fiber 10 facing upward, the vicinity of the end of the optical fiber is inserted into the groove of the fiber holding base 7, and the outer peripheral surface of the optical fiber and the inner wall of the groove are bonded using adhesive or the like.
It is fixed.

After adjusting the position of the fiber holder 7 so that the inclined end surface 11 of the optical fiber 10 faces the light-receiving surface 3 of the light-receiving element 1, the bottom surface of the fiber holder 7 is brought into close contact with the top surface of the circuit board 5, and the fiber The holding stand 7 is fixed to the circuit board 5.

Therefore, the optical signal propagated through the optical fiber 10 is
The oblique end surface 11 is almost totally reflected in a downward direction substantially perpendicular to the axis, that is, toward the light receiving element 1, and the light is emitted from the outer circumferential surface of the cladding layer facing the oblique end surface 11, and is emitted from the light receiving surface. 3
incident on .

As mentioned above, conventional light-receiving devices are devices in which the end face of the optical fiber is inclined, and the axis of the optical fiber is mounted close to and parallel to the top surface of the circuit board. This has the advantage that the light-receiving device can be made more compact than when it is mounted perpendicularly to the surface of the circuit board.

[Problem to be solved by the invention]

However, in recent years, light-receiving elements have improved frequency characteristics by reducing the capacitance. In other words, as the capacity becomes smaller,
In recent years, the light-receiving surface of light-receiving elements has become narrower.

On the other hand, in the conventional light-receiving device described above, the end face of the optical fiber is an oblique end face, so the output beam reflected from the oblique end face is expanded into a conical shape with a major axis in the axial direction of the optical fiber. It is opened and projected onto the light receiving surface 3.

Therefore, conventional light-receiving devices have a problem in that optical coupling efficiency decreases as the light-receiving surface becomes narrower.

Furthermore, when adjusting the optical fiber in an attempt to increase the optical coupling efficiency, the optical fiber may be brought too close to the light receiving element, causing it to hit the light receiving element and damaging the light receiving element.

The present invention was created in view of the above points, and an object of the present invention is to provide a light-receiving device that has high optical coupling efficiency and is small in size.

[Means to solve the problem]

In order to achieve the above object, the present invention, as illustrated in FIG. In a light-receiving device equipped with a light-receiving element l mounted with the light-receiving surface 3 facing upward in order to receive light, a concave reflecting mirror 20 having a desired concave surface is placed opposite the output end surface of the optical fiber 10 on the light-receiving surface. The structure is such that it is installed inclined in the direction of 3.

[Effect]

According to the present invention, the light emitted from the output end face of the optical fiber IO in a conical shape with the horizontal axis as its axis is projected onto the concave surface of the concave reflector, and is reflected by the concave reflector 20 in the direction of the light receiving element 1. . At this time, since the concave reflecting mirror 20 has a desired concave surface 21, such as a paraboloid of revolution, the light is focused on the light receiving surface 3.

That is, since the reflected light is focused on the light receiving surface, the degree of optical coupling between the optical fiber 10 and the light receiving element 1 is high even if the light receiving surface is narrow.

Furthermore, since it has a light condensing function, there is a certain distance between the light receiving element and the reflecting mirror at a position where optical coupling is optimal.

Therefore, there is no risk of damaging the light receiving element during adjustment.

〔Example〕

The present invention will be specifically described below with reference to the drawings. Note that the same reference numerals refer to the same objects throughout the plan.

FIG. 1 is a sectional view of one embodiment of the present invention, FIG. 2 is a diagram of another embodiment of the present invention, (al is a perspective view, (b) is a plan view of the main part, and FIG. 3 is a concave reflection It is a perspective view showing the concave surface of a mirror.

In FIG. 1, an electric circuit such as a receiving circuit and a light receiving element 1 such as a photodiode are mounted on the surface of a circuit board 5 made of ceramics or the like.

The light-receiving element 1 that receives optical signals has a small capacitance and is a chip type having a narrow light-receiving surface 3 on the front side, and has an electrode (not shown) provided on the entire back surface in close contact with the pattern 4B. Connect the ring-shaped electrode 2A on the surface to the circuit board 5.
It is connected to the terminal of another pattern 4A provided on the surface by wire bonding. That is, the light receiving element 1 is mounted on the circuit board 5 so that the light receiving surface 3 faces upward.

10 is, for example, a single mode optical fiber, the outer diameter of which is approximately 120 μ-, and the diameter of the core IOA is approximately 1
It is 0 μm.

The optical fiber 10 is an optical transmission line through which an optical signal is input to the light receiving element 1.

20 is a concave reflecting mirror having a rectangular plate-like outer shape formed by molding a polymeric material such as polymethyl methacrylate, and has a concave surface 21 formed of a paraboloid of revolution at the center of one plane part. This is provided. Further, a reflective film 22 is deposited on the surface of the two concave surfaces to increase the reflectance.

The diameter of the cut surface of this concave surface 21 needs to increase as the distance from the output surface of the optical fiber 10 increases, but generally, it is sufficient that it is around the outer diameter of the optical fiber 10. .

The curved surface of the concave surface 21 is not symmetrical to the axis Z of the paraboloid of revolution, as shown in detail in FIG. It is a parabolic antenna type.

The concave reflecting mirror 20 is installed on the circuit board 5 with the concave surface 21 facing the optical fiber 10 and tilting the concave surface 21 as desired in the direction of the light receiving surface 3. (In Figure 1, the concave reflector 2
A support structure for optical fiber 0 and a support structure for optical fiber 0 are not shown. ) Therefore, the light emitted from the output end face of the optical fiber 0 in a substantially conical shape enters the concave surface 21 , is reflected toward the light receiving element 1 , and is focused on the light receiving surface 3 .

Furthermore, since the optical fiber 0 can be mounted close to and parallel to the circuit board 5, the mounting work is easier than when the axis of the optical fiber is mounted perpendicular to the surface of the circuit board. , the light-receiving device becomes smaller.

FIG. 2 shows an embodiment in which an optical fiber array and a light receiving element array are optically coupled.

3 and 4 show an embodiment in which an optical fiber array and a light receiving element array are optically coupled.

In FIG. 1, a plurality of light receiving elements 1 (three in the figure) are arranged close to each other at equal pitches on the surface of a circuit board 5 mounted in close contact with the surface of a base 60 to form a light receiving element array. It consists of: Each light-receiving element l has a small capacitance and is a chip type having a narrow light-receiving surface on the front side, and has an electrode (not shown) provided on the entire back surface in a pattern 4B.
A ring-shaped electrode (not shown) on the surface
of another pattern 4A provided in parallel on the circuit board 5,
Connect each terminal with wire bonding.

15 is an elongated rectangular parallelepiped fiber array substrate made of silicon, for example, with etching etched on the bottom surface, etc.
A plurality of parallel grooves are provided at a pitch equal to the arrangement pitch of the light receiving elements 1. Then, the ends of the respective optical fibers 10 are inserted into the respective V-grooves and fixed with adhesive or the like to form the optical fiber array 100.

Note that after the optical fibers 10 are bonded, the output side end faces of the optical fiber array 100 are polished so that the output end faces of all the optical fibers 10 are on the same plane.

A rectangular parallelepiped fiber array support 16 made of the same material as the fiber array substrate 15 is bonded to the lower side of the end surface of the optical fiber array 100 opposite to the output end surface.

The side wall of the fiber array support stand 16 is brought into contact with the end surface of the circuit board 5, and the optical fiber array 100 is aligned so that the optical fiber 10 and the light receiving element 1 are on the same vertical plane, and the fiber array is supported. The bottom of the stand 16 is the base 6
It is fixed using adhesive.

Reference numeral 200 is a concave reflecting mirror array having a rectangular plate-like outer shape formed by molding a polymeric material such as polymethyl metatalate, and its length is equal to that of the optical fiber array 10.
The length of the fiber array substrate 15 is approximately equal to that of the fiber array substrate 15 of 0.0.

On one plane of the concave reflector array 200, there is a mountain (see Fig. 2).
A concave surface 21 formed of a paraboloid of revolution shown in FIG.
It is provided with a pitch equal to the pitch of.

Note that by depositing a reflective film on the surface of the concave surface 21, the surface of the concave surface 21 is
It increases the reflectance in

A reflective mirror array support plate 26 is bonded to the longitudinal end face of the concave reflective mirror array 200, and the bottom surface of the reflective mirror array support plate 26 is bonded to the surface of the circuit board 5. Note that the concave reflector array 200 is attached to the circuit board 5 such that each concave surface 21 faces the output end surface of the optical fiber 10;
In addition, the concave surface 21 is tilted as desired in the direction of the light receiving surface 3.

Therefore, the light propagating through each optical fiber 10 enters the concave surface 21 of the corresponding concave reflector array 200, is reflected by the concave surface 21 toward the light receiving element 1, and is focused on the light receiving surface 3.

The arrangement pitch of the V-grooves of the optical fiber array 10G can be set with high precision using lithography means, and the arrangement pitch of the concave surfaces 21 of the concave reflector array 200 can be set relatively accurately by molding. can.

Therefore, when the concave reflector array 200 is used as described above, the degree of optical coupling between the optical fiber array and the light receiving element array can be improved.

〔Effect of the invention〕

As explained above, the present invention is a light receiving device that optically couples an optical fiber and a light receiving element through a concave reflecting mirror, which has high optical coupling efficiency, is small in size, and prevents the light receiving element from being damaged during assembly. It has excellent practical effects, such as being fearless.

[Brief explanation of the drawing]

Figure 1 is a sectional view of an embodiment of the present invention, Figure 2 is a diagram of another embodiment of the present invention, (a) is a perspective view, (bl is a plan view of the main part, Figure 3 is a concave reflecting mirror) 4 is a sectional view of the conventional example. In the figure, 1 is a light receiving element, 3 is a light receiving surface, 5 is a circuit board, 10 is an optical fiber, 15 is a fiber array board, and 16 is a 20 is a concave reflective mirror; 21 is a concave surface; 22 is a reflective film; 100 is an optical fiber array; and 200 is a concave reflective mirror array.

Claims (1)

[Claims] An optical fiber (10) for transmitting an optical signal, and a light receiving device on a circuit board (5) parallel to the optical fiber (10) to receive the light emitted from the optical fiber (10). In a device equipped with a light-receiving element (1) mounted with its surface (3) facing upward, a concave reflecting mirror (20) having a desired concave surface is mounted opposite to the output end surface of the optical fiber (10). A light-receiving device characterized by being installed on a light-receiving surface (3) at an angle.